Light emitting device comprising a composite sialon-based ceramic material

Abstract

The invention relates to a light emitting device, especially a LED with a ceramic composite material essentially of the composition M 1−y A 2−x B x O 2−2x N 2+X :Eu y , where M is selected out of the group comprising Sr, Ca, Ba, Mg or mixtures thereof, A is selected out of the group comprising Si, Ge or mixtures thereof, B is selected out of the group comprising Al, B, Ga or mixtures thereof and x and y are independently selected from >0 to ≦1. This material has been found to be a two-phase composition, one phase being an amber to red emitting phase, the other one being a cyan to green emitting phase.

1 . Light emitting device, especially a LED comprising a ceramic composite material essentially of the composition M 1−y A 2−x B x O 2−2x N 2+x :Eu y , where M is selected out of the group comprising Sr, Ca, Ba, Mg or mixtures thereof, A is selected out of the group comprising Si, Ge or mixtures thereof and B is selected out of the group comprising Al, B, Ga or mixtures thereof and x and y are independently selected from >0 to ≦1. 
   
   
       2 . The light emitting device of  claim 1 , wherein the composite material comprises at least one amber to red emitting phase and at least one cyan to green emitting phase. 
   
   
       3 . The light emitting device of  claim 1 , x is ≦0.6. 
   
   
       4 . The light emitting device of  claim 1 , wherein the composite material comprises a phase of composition M(A,B) 2 (O,N) 3 :Eu and a phase of composition MA 2 O 2 N 2 :Eu. 
   
   
       5 . The light emitting device of  claim 1 , wherein the at least one amber to red emitting phase and/or at least one cyan to green emitting phase are essentially present in the composite material in form of ceramic grains to form a polycrystalline structure. 
   
   
       6 . The light emitting device of  claim 1 , wherein the d 50  of the grains of the at least one amber to red emitting phase and/or of the at least one cyan to green emitting phase is in the range of ≧1 μm to ≦50 μm. 
   
   
       7 . The light emitting device of  claim 1 , wherein the average grain size of the grains of the at least one amber to red emitting phase is larger than the average grain size of the grains of the at least one cyan to green emitting phase. 
   
   
       8 . The light emitting device of  claim 1 , wherein the emission maximum of the ceramic composite material is in the range of ≧520 nm to ≦650 nm. 
   
   
       9 . The light emitting device of  claim 1 , wherein the half-width of the emission band of the composite material in the visible wavelength range is in the range of ≧90 nm to ≦190 nm. 
   
   
       10 . A system comprising a light emitting device according to  claim 1 , the system being used in one or more of the following applications:
 Office lighting systems   household application systems   shop lighting systems,   home lighting systems,   accent lighting systems,   spot lighting systems,   theater lighting systems,   fiber-optics application systems,   projection systems,   self-lit display systems,   pixelated display systems,   segmented display systems,   warning sign systems,   medical lighting application systems,   indicator sign systems, and   decorative lighting systems   portable systems   automotive applications   green house lighting systems